This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Particulate methane monooxygenase (pMMO) is a 300 kDa membrane-bound enzyme that uses a catalytic copper-containing cluster to oxidize methane, the most inert hydrocarbon, to methanol. Characterization of the pMMO active center would provide fundamental insight into the chemistry of highly reactive species and could lead to the development of more efficient industrial catalysts or new methods for bioremediation. We recently solved the structure of pMMO from Methylococcus capsulatus (Bath), and propose experiments to identify the active site and to characterize the metal centers in detail. In addition, we have crystallized pMMO from Methylosinus trichosporium OB3b and plan to solve its structure. Because these membrane protein crystals do not diffract with a laboratory x-ray source and have large unit cell dimensions, ample time to collect diffraction data using third generation synchrotron radiation is essential to our research program.